Conventional galvanic dry cells for use in flashlights, toys or other sundry devices generally comprise a cylindrical container, such as a zinc anode can, with a depolarizer mix filling most of the container and having a carbon rod in the center which functions as the current collector for the depolarizer mix. The cells are generally sealed by inserting a support washer over the cathode depolarizer mix and then dispensing hot molten asphalt onto the washer thereby providing an asphalt seal for the cells while also providing an airspace above the depolarizer mix and below the asphalt seal to accommodate the discharge gases an exudate of the cells.
Although asphalt seals have been employed with some success in sealing galvanic dry cells, they do have a number of drawbacks or disadvantages. For example, several assembly procedures are required such as placing a support washer down into the cell, pouring an asphaltic pitch onto the support washer, placing a vent washer on top of the asphaltic pitch and then finally placing a terminal cap on top of the cell and locking it in place. The vent washer is usually required to prevent the terminal cap from becoming embedded in the pitch which could possibly result in forming a gastight seal which could prevent venting. In addition, it is possible that the inside surface of the container could become dirty due to mercury contamination, prior to dispensing the asphaltic pitch. This could result in a pseudo-seal which, over a period of time, could eventually lead to moisture loss from the cell and/or oxygen ingress to the cell because of insufficient adhesion of the pitch to the can or container. It is also possible that during the heating of the asphalt pitch to cause a meniscus to form at the can-asphalt interface, pin holes may form in the pitch as a result of expansion of the air in the void volume below the support washer which would allow moisture loss and/or oxygen ingress to the cell. Another disadvantage in the use of asphalt seals is that they physically take up a relatively large space in the cell thereby limiting the size of the airspace into which the reaction products of the cells can discharge. In addition, asphalt seals are not particularly suited for high temperature environments since the seal at the asphalt-can interface is subject to degradation at high temperatures which could possibly cause paths through which moisture (loss) and/or oxygen (ingress) could travel.
In the above-described cells, the venting of the gases from within the cell can take place through a porous current collector such as a carbon rod or the like. Although a properly prepared asphalt seal will effectively minimize electrolyte or moisture loss through evaporation and minimize air or oxygen ingress to the cells, the assembly and quality control techniques required to insure good seals are rather expensive and time consuming. The finished cells that do not meet the minimum quality standards for one reason or another are usually disassembled or detubed so that the raw cell components can be reused. However, in constructions where the container is adhered by asphalt or the like to the outer finish, recovery of the raw cell components is messy and expensive. Furthermore, when a top centering seal washer is employed as part of the finished cell, the detubing operation (removal of the outer jacket) may disturb this centering washer which in turn may cause the depolarizer mix contact to be somewhat loosened which could result in loss of amperage.
The object of the present invention is to provide a one piece closure for a dry cell wherein the closure replaces several components of the conventional cell and is capable of sealing the cell.
Another object of the present invention is to provide a one piece closure for galvanic dry cells having a peripheral skirt or apron adapted for sliding upon and being adhesively secured to the upper rim at the open end of the container (anode) of the cell and a centrally disposed tubular neck adapted for sliding over and being adhesively secured to the current collector (carbon rod) of the cell.
Another object of the present invention is to provide a closure for a galvanic dry cell having a top surface contour fabricated to conform to the bottom surface contour of the metal terminal cap of the cell so as to provide a maximum airspace above the depolarized mix of the cell and below the closure.
Another object of the present invention is to provide a closure for a galvanic dry cell having a peripheral skirt adapted for snugly sliding upon and adhesively securing to the upper rim at the open end of the container (anode) of the cell and a centrally disposed opening adapted to slide over the center metal terminal cap of a two-piece terminal cover with a portion of the inner bottom surface of the closure adhesively secured to the top surface of a radially outward flange depending from the bottom of the metal terminal cap.
Another object of the invention is to provide a closure for a galvanic dry cell having a peripheral skirt adapted to snugly slide upon and be adhesively secured to the upper outer rim at the open end of the cell container that has been necked or crimped in to allow for the thickness of the skirt of the closure thereby maintaining an overall uniform container diameter for the cell and having a centrally disposed opening adapted to slide over and be adhesively secured to the current collector of the cell.
Another object of the invention is to provide a closure for galvanic dry cells which can easily and inexpensively be assembled on such cells.